Telephone handsets typically comprise complementary upper and lower housing members that mate at their perimeters to form a hollow handset housing. The handset contains microphone and loudspeaker transducers for respectively transmitting and receiving audible signals. Over the years, technology has improved telephone handset construction making them less expensive, more rugged, easier to assemble, and providing higher sound quality than earlier models.
In many telephone handsets, relatively complex and labor intensive schemes exist for affixing the transducers to the lower housing member (deck). Most schemes require the use of a special plate or cup-shaped retainer that is fastened to the deck with several screws--typically two or more. Examples of such design are shown in U.S. Pat. Nos. 4,124,785 and 4,319,095.
Holding the deck and shell members together frequently requires the use of bonding materials or epoxy adhesives that need a 24-hour curing period. Such an interval is inconsistent with modern manufacturing techniques such as Just-In-Time (JIT) fabrication that reduces factory inventory and, hence, lowers cost. An example of a telephone handset that uses bonding materials in its construction is shown in U.S. Pat. No. 4,712,236. Alternatively, interlocking hook and latch members at the extremes of the handset are frequently used to hold those members together. Such interlocking, however, does not provide good mechanical joining of the deck and shell which readily separate from each other when the handset is dropped.
The control of acoustic leakage between transmitter and receiver transducers is important in regulating background noise. Frequently, flexible gaskets are used to provide acoustic seals and rely on auxiliary mechanical means to maintain pressure on the gasket. Generally, only the front surface of the transducer is sealed and uniform mechanical pressure around the transducer is needed to eliminate acoustic leakage. An example of such a technique is shown in U.S. Pat. No. 4,163,875 where the gasket used to seal the front surface of the transmitter also serves to hold the transmitter and cup-shaped member together. In that patent, however, the acoustic seal at the transmitter is maintained by mechanical forces transferred to the shell. In turn, the shell transfers these forces to interlocking hooks and latches that are positioned at the extremes of handset. The mechanical seal at the receiver is maintained by a cup which covers the receiver and has a rim that is rotated into engagement with projections molded in the deck. The cup not only represents an additional part, but internal projections complicate the molding process while rotational engagement complicates the assembly process.
Accordingly, it is an object of the present invention to provide a telephone handset construction that facilitates assembly at reduced cost.
It is another object of the invention to provide good acoustic seals for the transmitter and receiver without reliance on mechanical fastening apparatus.
It is yet another object of the present invention to provide a design which does not require the use of bonding materials and yet is rugged enough to withstand repeated drops without separating.